Firstly i would like to praise the writers. This mystery has a lot of research put into it. Attention to the cultural and historic context is amazing. Even all the locations on the Arensburg map are correct. Kudos!
When i GM "historical" games, games that take place in real world, I usually prefer to add some real life props into games myself: maps, persons and stories. Some old photos and maps can work wonders with player`s immersion. Since i am Estonian myself this adventure immediately sparked my interest to do some more background research on 1890 - 1900s Ösel (Saaremaa).
To run this adventure i compiled a bunch of old photos from Ösel and Arensburg. I also designed my own version of Kaali village map.
In order to avoid lengthy posts i piled all the information on my site:
https://rpg.meelismikker.eu/vaesen/fall ... ackground/
At the end of the post there are links to different websites that can be helpful to GMs wanting to run adventures in 1800's Estonia.
I will post a few pictures here as a teaser. Enjoy!
Here is the picture of Kaali Crater:
This is the Von Kaiserling's house
Sanatorium where the people used to take mud-baths:
My take on Kaali village map: